JP2002525652A - How to use the adjustment exposure mask - Google Patents

Abstract

(57) A photolithographic method comprising providing a layer of photoresist material (250) on a substrate (240). Radiation is transmitted to the photoresist material through a layer of absorbing material that absorbs radiation with a transmission proportional to the thickness of the absorbing material (220). A surface relief structure is formed in the absorbing material such that the photoresist material is only partially exposed to a pattern corresponding to the surface relief shape. Thus, when the photoresist material is developed, it has a surface relief structure corresponding to the surface relief structure in the absorbing material. Thereafter, when the developed photoresist material and the target substrate are etched, a surface relief structure in the target substrate corresponding to the surface relief structure in the developed photoresist material is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001] The present invention relates to an adjustment exposure mask used in a conventional photolithography method. The mask has a layer of material that absorbs radiation proportional to its thickness. Furthermore, the absorbing material is shaped such that the radiation dose absorbed by the mask varies on its surface. Using the adjustment exposure mask according to the present invention,
Continuously variable surface topography on the target substrate
ace topography).

BACKGROUND OF THE INVENTION In general, conventional photolithographic methods are used to create various fine structures ranging from semiconductor devices to microlens arrays. According to typical conventional photolithographic methods, a target substrate is coated with a photoresist material (ie, photoresist). Thereafter, portions of the photoresist are exposed to radiation through a mask. The mask embodies a design that completely blocks radiation from irradiating selected portions of the photoresist, with all other portions of the photoresist being exposed. This type of photolithographic mask, which either completely blocks or completely transmits the incident light, is now called "binary"
"Photolithography mask.

[0003] After exposure, the exposed portions of the photoresist are removed by a chemical reaction, leaving the unexposed portions (or vice versa). Thereafter, the entire surface, including both the remaining portion of the photoresist material and the uncovered portion of the underlying target substrate, is etched using conventional etching methods such as ion milling. This etching method etches an uncovered portion of the target substrate to form a desired structure in the substrate.

However, one problem with such conventional photolithographic methods is that
That they only form structures with a "binary" topography. That is, these methods produced only structures with substantially two distinct heights or levels, with the photoresist removed at lower levels and the remaining photoresist material coated the substrate at higher levels. (Defects in photolithographic methods, such as diffraction, cause some variation between the levels of their interfaces, but these variations are weak and cannot be controlled because they typically benefit the structure. )

[0005] With the increasing demand for more complex fine structures, various solutions to this problem have been sought. One well-known solution to this problem has been proposed, for example, in US Pat. Nos. 4,895,790, 5,161,059 and 5,218,4 to Swanson et al.
No. 71 is a multi-stage photolithography method discussed in each specification. This method, each shown in FIG. 1, creates a multi-level structure using repeated photolithographic cycles.

To discuss this method in more detail, a first method cycle begins with a target substrate 110 covered with a layer 120 of photoresist. Photoresist 120 is exposed to ultraviolet light through first binary mask 130. Thereafter, the exposed portions of the photoresist 120 are removed, and the uncovered portions of the target substrate are etched using a dry etching method. This first method cycle creates a two-level structure.

To obtain a multi-level structure, the two-level structure undergoes a second method cycle.
The target substrate 110, which currently has two levels, includes a second layer 14 of photoresist.
0. Thereafter, portions of this second layer of photoresist 140 are exposed to ultraviolet light by a second binary mask 150. The exposed portions of the second photoresist layer 140 are removed, and a second dry etching method etches the uncoated portions of the target substrate 110 to create a structure with four distinct levels. Additional photolithographic cycles can be used to generate structures with, for example, 8, 16, and 32 different levels.

[0008] However, this multi-step photolithography method has several problems. First, the method requires a conventional photolithography method that is performed over a long period of time, which is time-consuming and labor-intensive. In addition, each binary mask must be carefully aligned with the substrate so that its exposure exactly matches the structure formed by previous photolithographic methods. Moreover, this multi-step photolithography method can only produce structures with discrete or "dual" levels. This method cannot be used to produce structures with continuously variable, or "analog" topography, which is technically desirable.

[0009] Therefore, other methods have been proposed to generate fine structures with continuously variable topography. One type of method, the "direct write" method, is to etch or remove material from a target substrate using a high energy density, tightly controlled beam to form the desired structure. To adhere. Alternatively, such a beam is used to form a desired topography in a layer of photoresist material prior to a conventional etching method. The direct writing method can be performed with various high energy beams, such as a focused ion beam, a high energy laser beam, and an electron beam. For example, U.S. Pat. No. 5,541,411 to Lindquist et al., And U.S. Pat.
See US Pat. No. 48,419 and US Pat. No. 5,811,021 to Zarowin.

However, the direct writing method also has a problem. This method is time consuming because each topography feature must be cut individually, and is often impractical for making large devices (ie, devices with an area greater than a few square millimeters). In addition, unlike photolithographic methods, devices can only be individually generated by direct writing, making it impractical for any purpose that requires more than some devices. In addition, the direct writing method requires expensive equipment such as a focused ion beam generator or an electron beam generator.

Other methods have been proposed for obtaining continuously variable topography by a photolithographic method using a dedicated mask. For example, US Patent No. 5 to Gal
, 310,623 and 5,482,800 teach the use of "grayscale" lithographic methods. This method uses a binary mask, similar to conventional lithographic methods, but the opaque portions of the mask are made up of very small pixels (eg, 1-100 microns). These pixels are
Similar to that produced by the photocopier, the entire image provided by the mask is arranged to be a grayscale image. That is, such small pixels are arranged such that the percentage of light transmitted through the mask as a whole varies on its surface.
However, in this method, the mask is a reduced stepper (re) with inherently limited fidelity.
The image must be reproduced by an induction stepper. Thus, due to practical issues, the application of this grayscale lithography method is typically limited to relatively small devices (eg, 0.5 inches).

Yet another type of photolithographic method for obtaining continuously variable or analog topography is the holographic / interferometric type method. The method selectively exposes a photoresist to a radiation pattern caused by interference between multiple coherent beams of radiation. However, in this method, it is difficult to appropriately set the interference pattern, and thus, the achievable surface relief structure is limited. Moreover, the fact that only one device can be produced by each holographic / interferometric method makes this method impractical for any use that requires several more devices.

Yet another photolithographic method for producing continuously variable topography is described in US Pat. Nos. 4,567,104, 4,670,366, and 4,8 to Wu.
Nos. 94,303, 5,078,771 and 5,285,517. As described in those patent specifications, this method is formed from specially doped / implanted high energy beam sensitive (HEBS) glass that becomes opaque in proportion to exposure to electron beam radiation. Use the mask provided. Thus, the mask is made by exposing portions of the glass to varying electron beam radiation doses such that the opacity of the mask varies on the surface. However, this method has the disadvantage that the HEBS glass has a very low sensitivity to the electron beam to be exposed. Therefore, it takes a relatively long writing time, a production time, and a high cost to produce a mask.

OBJECTS AND SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a photolithographic method capable of easily, quickly and inexpensively producing structures or devices with continuously variable topography. It is a further object of the present invention to provide a photolithographic mask that produces continuously variable topography by a single, photolithographic method step. It is a further object of the present invention to provide a method for forming a photolithographic mask that produces a continuously variable topography with a single photolithographic method step.

According to the present invention, a single photolithography step method produces a structure with a continuously variable (ie, analog) surface topography. The present invention utilizes an adjusted exposure mask with a light absorbing material that varies thickness continuously over the original surface of the mask. Due to the continuous variation of the thickness of the light absorbing material, the amount of light transmitted through the mask is spatially adjusted accordingly. Thus, in the photolithography method using the adjustment exposure mask, the exposure and subsequent removal of the photoresist continuously vary on the surface of the target substrate.

The adjustment exposure mask for photolithography according to the present invention can be formed by using, for example, the above-described direct writing method (for example, partial electron beam exposure). One preferred method of forming the adjustment exposure mask uses a material that absorbs radiation of a desired wavelength, such as ultraviolet light. This layer of absorbent material, which is about a few microns thick,
The target substrate is formed over a thicker layer of material that transmits the desired wavelength. Thereafter, a layer of electron beam resist is formed over the absorbing material layer. The electron beam then partially exposes the e-beam resist, creating a surface relief structure in the resist. Thereafter, the surface relief structure is transferred into a thin layer of absorbent material to form a mask according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One preferred photolithographic method according to the present invention is illustrated in FIGS.
The following is a description with reference to c). In these figures, the adjustment exposure mask 210 includes a layer 220 of a material that absorbs ultraviolet light, such as SiO. This layer 220 of absorbent material has a continuously varying surface relief structure. (The specific surface topography of the absorbent material 220 is generated by the equation discussed in detail below.) The absorbent material 220 is preferably very thin (eg, a few microns thick) and the base 230 for mechanical robustness. It is fixed to. The base 230 is formed from a material that transmits ultraviolet light, such as quartz. Thus, the adjustment exposure mask 210 absorbs ultraviolet light by surface relief topography of the absorbing material 220 with the amount of absorption directly related to the thickness of the absorbing material 220.

Then, using the specific absorption pattern embodied in the adjustment exposure mask 210,
It is possible to control the exposure of the photoresist material by a photolithographic method. As shown in FIG. 2A, the adjustment exposure mask 220 is located between the ultraviolet light source and the target substrate 240. The target substrate 240 is covered with a layer 250 of a photoresist material. Conditioned exposure mask 210 causes different (ie, non-uniform) UV transmission through resist to resist material 250. As will be appreciated by those skilled in the art, the more ultraviolet light that reaches the resist material 250, the greater the exposure of the resist material 250. Thus, the exposure of the resist material 250 varies on its surface with a profile corresponding to the absorption pattern of the adjustment exposure mask.

After developing the resist material 250, it has a surface relief structure that is a function of the degree of exposure of the resist material 250 to ultraviolet light, as seen in FIG. 2 (b). This surface topography instead corresponds to the topography of the absorbing material 220. Then, the surface relief structure of the photoresist material 250 is transferred to the target substrate 240 by a conventional etching procedure such as dry etching using an ion mill or a reactive ion etcher (see FIG. 2C). Thus, it is possible to produce a structure with the desired continuously variable surface relief using the adjusted exposure mask according to the invention. However, as will be appreciated by those skilled in the art, there are several factors that must be considered in order to properly generate and implement the adjusted exposure mask according to the present invention. Each of these factors is discussed in detail below.

The first factor is the ability to faithfully map surface relief structures (eg, multi-level / analog surface profiles) formed in the photoresist onto the target substrate. This may be accomplished by various well-known etching methods, such as dry etching, chemically assisted etching, and wet etching. Ion milling and reactive ion etching are two examples of such known etching methods that can etch both photoresist materials and most desired substrate materials.

One of ordinary skill in the art will recognize that by controlling the photoresist etch rate relative to the target substrate etch rate, the vertical dimension of the structure formed in the developed photoresist can be measured as appropriate. Would. That is, the measure of the structure formed in the target substrate can be controlled by either selecting the measure of the structure formed in the developed photoresist, or selecting the relative etch rate of the photoresist with respect to the substrate. is there. (Eg “Fabrication of Micro-Opt
ical Devices ”by WW Anderson et al., Conf. on Binary Optics, NASA Co
nference Publication 3227, February 23-25, 1993)

For example, in reactive ion etching, it is possible to increase the photoresist etch rate by increasing the oxygen level in the etching plasma. The ratio of the substrate etch rate (Rs) to the photoresist etch rate (Rp) is called selectivity and is given by Equation 1: S = Rs / Rp [1] As seen in FIG. Assuming that the height of the resist structure 310 is H, the height of the structure transferred to the substrate 320 is HS.

A second factor to be considered is the ability to create a relief structure (eg, a multi-level or analog surface profile) in the photoresist. In a single photolithographic method step to create a multilevel or analog structure, some or an intermediate amount of photoresist must remain after exposure and subsequent development. Since most photoresist materials have a binary type of exposure reaction, this is typically achieved by underexposing or partially exposing the photoresist layer. For example, in a typical positive photoresist material, the unexposed areas are hardly affected during development, while the exposed portions are almost completely removed during development.

This exposure reaction information is generally called a contrast curve or a γ curve of the resist material. An example of such a curve is shown in FIG. This curve shows the Shipley MF-3
21 is a Shipley photoresist S3813 developed with a developer 21. (Chipley is a well-known supplier of photoresist and developer materials.)
From this curve, it can be seen that an energy density of 30-100 mJ / cm ² provides an intermediate level of residual resist, which allows the formation of complex surface relief structures with this photoresist. Any non-linearities in the contrast curve can be corrected for in the mask design. However, this type of photoresist has high contrast and therefore high non-linearity, which makes it difficult to use to obtain multi-level analog photoresist structures.

As will be readily appreciated by those skilled in the art, it is preferable to use a photoresist material that does not have high contrast, and to provide a photoresist material with a contrast curve that has a linear characteristic in the applicable energy range. It is most preferred to use. Shipley 1000 series of photoresist materials have been shown to produce significant linear response. Shipley photoresist S partially exposed
The structure resulting from the development of TR1110 is shown in FIG. This structure was created using an analog mask formed from HEBS glass by the method described above. The mask had a linear transmission profile and the resulting photoresist structure was measured using a Tencore profilometer. Some AZ resists give similar results. Although these are two brands of well-known photoresist materials, any conventional photoresist material can be used in the photolithographic method according to the present invention. As noted above, the photoresist material preferably has a contrast curve that is as linear as possible over the applicable energy range.

A third factor is the ability to spatially adjust the energy of exposure radiation (eg, ultraviolet light) to produce the desired multi-level / analog surface profile of the photoresist. This is achieved by varying the thickness of the absorbing material of the mask. As is known to those skilled in the art, the energy input into the absorbing material (Ei)
The relationship between the outputted corresponding energy from the absorber _{(E 0),} as a function of the thickness of the absorbing material, wherein ^{_{2, E 0 = E i e}} [-4πk (λ) d / λ] [2] ( Where d is the thickness of the absorbing material and k is the imaginary part of the refractive index of the material, which is a function of the wavelength (λ) of the light and is often given by the absorption coefficient.
From this it can be seen that the proportion of energy transmitted to the absorbing material can be controlled by varying the thickness d of the absorbing material.

Interpreting Equation 2 with the thickness d and the spatial dependencies x and y gives the form that an absorbing material that produces a given transmission must be incorporated. d (x, y) = [− λ / 4πk (λ)] ln [E ₀ (x, y) / E _i ] = [− λ / 4πk (λ)] ln [T (x, y)] [3 From Equation 3, it will be appreciated that in order to generate a linear transmission function, the thickness of the absorbing material must have a natural logarithmic profile. Thus, when selecting an absorbing material for the mask, two characteristics must be considered.

First, the absorbing material must have an absorption coefficient such that the required thickness of the absorbing layer can work. From experiments, the minimum transmittance of the absorbing material is given by T = E ₀ / E _i > 0.25 [4]. This sets a limit on the maximum value of the ratio k (λ) d / λ in the exponent of Equation 2 where k (λ) d / λ <0.22 [5]. Therefore, a reasonably low thickness d must be allocated.

[0029] A factor that usually influences this decision is the ability to repeat a given thickness profile. The materials selected to facilitate the etching method and the etching characteristics of the equipment used are key to the repeatability of the method. However, for most materials that can be etched, typically with a reactive ion etcher or ion millable material using fluorine chemistry, an acceptable range of ratios, 0.5 microns <d <1.5 microns [6] Then, d must be selected as 0.15 <k (λ) / λ <0.44 [7].

For example, SiO is one material that has this tolerance at wavelengths of ０．３0.39 microns <λ <〜0.44 microns. This wavelength range encompasses the H and G lines of the mercury arc lamp commonly used in conventional lithographic methods. However, as will be appreciated, using different etching chemistries, such as chlorine-based chemistries, or different etching techniques, such as wet chemical etching, can affect the range shown in Equation 6. Of course, those skilled in the art will of course understand how to improve the range shown in Equation 6 accordingly.

A second feature to consider when choosing a suitable absorbent material is the mechanical properties in thin film coating form. The absorbing material must be able to grow, sputter or deposit on the base substrate in several ways in a uniform manner such that it adheres to the base substrate. The mask is a contact mask
If used as, it must withstand periodic cleaning. Furthermore, the absorbing material must not degrade over time due to exposure to radiation during use.

A fourth factor in implementing the conditioning exposure mask according to the present invention is the ability to fabricate the surface relief structure of the absorbing material required to make the desired conditioning in the exposure of the photoresist. As will be appreciated by those skilled in the art, the desired surface topography of the absorbing material can be produced by any suitable conventional technique, such as conventional lithographic methods and the direct writing methods discussed above. For example, if the absorbing material has a "binary" multi-level profile, that profile can be formed using the multi-step lithographic method shown in FIG. Alternatively, if the absorbing material has an "analog" continuously variable profile, that profile can be formed using any direct-write method or HEBS glass discussed above.

To obtain an analog surface relief structure, the required topography is formed on the absorbing material, preferably by the direct writing electron beam (e-beam) method described above, as shown in FIG. In this method, the absorbing material 610 is located on the base substrate 620 and is covered with a layer 630 of e-beam resist material. The electron beam sensitive resist is partially exposed by the electron beam. The amount of charge delivered to the e-beam resist varies depending on the topography created in the absorbing material 610.
FIG. 7 shows the result of a change in the amount of charge sent to the e-beam sensitive resist by the direct writing method. In this figure, the 17-level surface relief structure is e-
It is formed in a beam resist material. This structure can then be faithfully mapped to the absorbing material under the e-beam resist. The use of an e-beam sensitive resist material provides shorter write times with methods other than electron beam, such as the HEBS glass approach.

One alternative for creating the desired surface relief structure with an absorbing material is to sputter the material onto a base substrate using a focused ion beam (FIB).
This method is attractive because it requires fewer processing steps than the direct electron beam writing method. However, it has significant drawbacks, and generally less than 3 cubic microns per minute of focused ion beam can be removed or deposited. In other words, even a very small device will require a relatively long writing time to generate the adjustment exposure mask. This writing time can be reduced by choosing an absorbing material with a relatively high absorption coefficient, such as a metal. This reduces the volume of material to be transferred to or from the base substrate.

Another alternative to forming a tailored exposure mask, perhaps the most economical, is
Use the "grayscale" approach described above. For repeating patterns whose dimensions are smaller than the field size of the stepper, the pattern can be stepped over the entire mask and repeated to create a large contact or stepper mask. For patterns larger than the field size of the stepper, it is possible to use a series of masks that are aligned with the stepper to create a larger unique pattern.

In one preferred embodiment of the present invention, the conditioning exposure mask includes a transparent protective layer formed on the absorbing material. Thus, as shown in FIGS. 8A and 8A, the adjustment exposure mask has a base substrate 810, a layer 820 of an absorbing material having a desired surface relief structure, and a transparent protective layer 830. The transparent protective layer 830 can be applied in any manner (eg, deposition, sputtering, growth, etc.).

[0037] The transparent protective layer offers at least three important advantages. First, it protects the absorbing material from contact lithography, from photoresist during cleaning, and generally from the environment. In some embodiments, the protective layer can be applied thick enough to create a flat outer surface of the mask, as shown in FIG. 8 (a). Flattening (or almost so) the outer surface of the conditioning exposure reduces small gaps where contaminants can adhere.

Second, when choosing a material for the protective layer that has the same or nearly the same coefficient as the absorbing material, it reduces or eliminates phase distortion caused by the topography of the absorbing material. This advantage can be important for producing small feature structures that are almost the resolution limit of the chosen lithographic method.

A third advantage provided by the transparent protective layer is to improve the functionality of the mask by providing a basis on which a phase adjustment function can be added to the mask. That is,
By providing a surface relief structure in the transparent coating, as shown in FIG. 8 (b), it is possible to add complex phase functions to the mask. The adjusted exposure mask thus obtained adjusts both the amplitude and the phase of the illumination source in a lithographic method. More specifically, the amplitude of the radiation is adjusted by the layer of the absorbing material, while the phase is adjusted by the surface relief structure of the transparent layer. The phase and amplitude layers of the mask should be aligned by standard alignment techniques, but this shape enhances the resolution of lithographic methods, as is well known in the art of phase shift masking techniques.

This embodiment of the adjustment exposure mask can also be used to create complex patterns desired for holographic lithography. Conventional holographic lithography relies on coherent summing of light beams or orders. The complexity of the patterns that can be produced simultaneously is limited by the order of the light that can be interfered and the intensity and phase control of each order. Such light orders are typically created using bulky macro optics such as mirrors and prisms.

It is possible to construct complex amplitude and phase adjustment exposure masks according to the present invention to generate arbitrary orders with various amplitude and phase amounts. This use produces very complex patterns by holography. Since holographic lithography has a very large depth of focus (a few millimeters), it enables lithography with high resolution on curved surfaces. Thus, for example, diffractive optics, Fresnel optics, refractive micron lens arrays, or surface relief anti-reflective structures can be added to the curved surface of a bulky refractive lens. The high resolution of holographic lithography provided by this embodiment of the adjusted exposure mask also allows the mask pattern to be measured by image reproduction of the pattern, as is often done in steppers. Holographic lithography is a non-visual far-field lithography, so the "gray scale" discussed above
It should further be noted that the approach can be used to adjust the amplitude of the transmitted radiation instead of the absorbing material layer.

While the above-discussed modified exposure mask embodiment includes a molded layer of absorbent material formed on a base substrate, the invention is not limited to this embodiment. For example, a sufficiently strong (ie, mechanically strong) absorbent material layer can be used alone as a conditioning exposure mask without a base substrate. The absorbing layer can be formed as a part of a bulky mask substrate. For example, if the HEBS glass was completely overexposed (and thus darkened), the darkened material would be trapped in a layer several microns thick just below the surface. Surface relief structures can be etched into this darkened layer to form a tailored exposure mask according to the present invention.

Although particular embodiments of the present invention have been described above, it will be appreciated that the present invention is not limited to these embodiments. For example, SiO and quartz have been mentioned as materials for the absorption layer and the base substrate, respectively. However, it will be apparent to those skilled in the art that many alternative materials may be used for both, depending on the type of photolithographic method used. Also, those skilled in the art will recognize that the present invention is applicable to a variety of lithographic methods using any wavelength of radiation (eg, X-rays, visible light, etc.).

Further, while the adjustment exposure mask has been described in detail for a lithographic method, those skilled in the art will appreciate that the adjustment exposure mask according to the present invention may be used for other purposes. That is, the adjustment exposure mask can be used as an amplitude / intensity / energy adjuster in other applications.

Thus, while the present invention has been described in combination with various embodiments, these embodiments are illustrative only and should not be regarded as limiting. Many alternatives, modifications, and variations that fall within the scope of the appended claims will be apparent to those skilled in the art in light of the foregoing detailed description.

[Brief description of the drawings]

FIG. 1 is a diagram schematically illustrating a conventional photolithography method.

FIG. 2 is a schematic diagram illustrating a photolithography method according to one embodiment of the present invention.

FIG. 3 is a diagrammatic representation of a substrate etch rate (Rs) relative to a photoresist etch rate (Rp).

FIG. 4 is a Shipley photoresist S3813 developed with Shipley MF-321 developer.
The figure which showed the contrast curve of.

FIG. 5 shows a structure generated by developing a partially exposed Shipley photoresist STR1110.

FIG. 6 illustrates a direct-write electron beam method for forming an adjustment exposure mask according to one embodiment of the present invention.

FIG. 7 is a diagram showing a result of a change in the amount of charge sent to an electron beam sensitive resist material.

FIG. 8 is a diagram showing an embodiment of an adjustment exposure mask according to two other embodiments of the present invention.

[Procedure amendment]

[Submission date] May 7, 2001 (2001.5.7)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

──────────────────────────────────────────────────続 き Continuation of front page (81) Designated country EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE ), OA (BF, BJ, CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP (GH, GM, KE, LS, MW, SD, SL, SZ, TZ, UG, ZW), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AE, AL, AM, AT, AU, AZ, BA, BB, BG, BR, BY, CA, CH, CN, CR, CU, CZ, DE, DK, DM, EE, ES, FI, GB, GD, GE, GH, GM, HR, HU, ID , IL, IN, IS, JP, KE, KG, KP, KR, KZ, LC, LK, LR, LS, LT, LU, LV, MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, SE, SG, SI, SK, SL, TJ, TM, TR, TT, TZ, UA, UG, US, UZ, VN, YU, ZA, ZW (72) Invention Barry, S. McCoy, Alabama, U.S.A., Huntsville, Import, Circle, 205, Men's, Optical, Limited, Liability, Company (72) Inventor Gerald, Tack Alabama, U.S.A., Huntsville, Import, Circle, 205, Men's, Optical, (72) Inventor Scott, Miles Alabama, U.S.A., Huntsville, Import, Circle, 205, Men's, Optical, Limited, Liability, In-Company (72) Inventor Bruce, Peters Alabama, U.S.A. , Huntsville, Import, Circle, 205, Men's, Optical, Limited, Liability, Company F-term (reference) 2H095 BA01 BB01 BB10 BC05 BC27 2H096 AA24 AA28 BA01 EA30 2H097 GB0 0 JA03 JA04 LA10 5F046 AA25 CB17 LA18

Claims (1)

[Claims] Providing a layer of photoresist material on a target substrate, (1) absorbing radiation having a transmittance proportional to the thickness of the absorbing material, and (2) surface relief formed therein. Partially exposing the photoresist material by transmitting radiation through the layer of absorbing material having a structure, developing the photoresist material and developing corresponding to the surface relief structure in the absorbing material Forming a surface relief structure in the developed photoresist material; and etching the developed photoresist material and the target substrate to provide a surface relief in the target substrate corresponding to the surface relief structure in the developed photoresist material. Forming a structure.